Enterprises want wireless communications for their employees within their work place (office buildings and warehouses, retail facilities, etc) and in the field. Cell phones are satisfactorily used by employees for wide area mobile communications, but coverage within buildings is not always adequate. Coverage problems arise when a user attempts to use a cell phone inside a building. For example, electromagnetic signals, such as radio frequencies used by cellular phones, are unable to fully propagate through walls, metalized glass and other common building materials that separate the inside of a building from an outside environment. As a result, the user may experience a degradation of service or may be precluded entirely from sending or receiving information while inside a building or other structure.
One solution to poor in-building cellular coverage has been to install a wireless private branch exchange (PBX) and to issue employees wireless WiFi enabled session initiated protocol (SIP) phones for mobile communications within buildings. However, this requires the enterprise to purchase two mobile devices for each employee—a cell phone for wide area communication, and a WiFi SIP phone for communication within the work place—which may be a substantial expense. In addition, this requires employees to carry multiple mobile devices, each typically having different contact number associated with it. Thus, callers must dial a different number to reach the employee, depending on the location of the employee (e.g., in the work place or in the field).